Method for producing fine alumina particles using multi-carbide ginding media

ABSTRACT

Grinding media, including shaped media such as spheres or rods ranging in size from about 0.5 micron to 100 mm in diameter, are formed from a multi-carbide material consisting essentially of two or more carbide-forming elements and carbon, with or without carbide-forming elements in their free elemental state. The media have extremely high mass density, extreme hardness, and extreme mechanical toughness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 60/453,427 filed on Mar. 11, 2003 and entitled SPHERES IMPARTINGHIGH WEAR RATES, incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to the field of grinding mediacomposition, and more specifically to multi-carbide materials for use asgrinding media formed in the shape of spheres or other shaped media.

BACKGROUND OF THE INVENTION

Carbide materials are well known in the art of material science. Theyinclude a range of compounds composed of carbon and one or morecarbide-forming elements such as chromium, hafnium, molybdenum, niobium,rhenium, tantalum, thallium, titanium, tungsten, vanadium, zirconium,and others. Carbides are known for their extreme hardness with hightemperature tolerance, properties rendering them well-suited forapplications as cutting tools, drilling bits, and similar uses.Multi-element carbides are known for their improved toughness andhardness relative to single element carbides. Single element carbidesare typically used with a metal binder to impart toughness.

Multi-carbides are formed by combining two or more carbide-formingelements with carbon. Some multi-carbides have other non-carbide formingelements in the composition, such as nitrogen, but are here referred tosimply as multi-carbides since the dominant components arecarbide-forming elements. For example, a combination of tungsten andtitanium with carbon and nitrogen would be such a multi-carbidematerial. Some multi-carbide compositions are formed with a deficiencyof carbon resulting in some small percentage of carbide-forming elementnot being converted to a carbide and instead remaining as uncombinedelemental metal. These combinations can enhance certain of the favorablequalities of carbides, with some combinations increasing hardness,others increasing toughness, and so forth. Very small variations incomposition can greatly affect the material's properties. Many of thesevariations are well understood by practitioners of the art and are amplypublished.

Spheres and solid bodies of other specific shapes, whether of carbide ormulti-carbide, are difficult to manufacture due to the very propertiesthat make them useful. Their high melting point necessitates a powerfulenergy source with difficulty in temperature regulation and effect, andtheir hardness makes them costly to machine.

For example, a primary manufacturing method used to manufacture carbidesis to place the elements to be fused on the recessed surface of a largeelectrode. A very high current is passed from that electrode through thematerial and into another electrode in proximity, subjecting thematerial to the heat of an electric arc. This process is effective infusing the materials, but causes inconsistent mixing of the elements inthe compound and some uncontrolled loss of material due to vaporization,phenomena that can greatly compromise the properties of the resultingcompound in uncontrolled and unpredictable ways. Hardness is also achallenge, as the manufacturing process results in an irregularly-shapedlump of resulting compound that is generally a few inches in diameter,colorfully known as a “cow chip”. The “chip” is very hard, and is workedinto smaller shapes only by percussive shocking or other crushing methodthat cleaves the chip into useful sizes. These processes leave smallcracks in the finished product that greatly reduce both its hardness andits mechanical toughness. Re-melting of the material after crushingimposes high cost, and cannot efficiently achieve regular particle sizesor shapes. Consequently, although carbide is available in small spheresand other preferred shapes, those spheres are not optimally composed,they are irregularly sized, they are expensive, and they are lacking ineffectiveness.

The known art currently does not have a process whereby multi-carbidematerials can be formed into small and regular shapes without loss ofoptimized properties due to process variation in manufacture ordegradation of material during shaping.

Reducing of particles, also known as comminution, is a very old art,practiced for example by the ancients to produce flour from grain bystone wheel grinding. Later practices required smaller and more regularpowders for a variety of industrial applications, and more refinedtechniques were developed to produce those products, such as mediamilling. Modern technologies and practices now demand ever-finerparticles, measured in microns, thousandths of microns, and evenangstroms; and with greater regularity of particle size and purity atthese reduced dimensions.

Just as stone wheel grinding could not reliably provide the powdersneeded for earlier industrial processes, current media mills and similartechnologies cannot reliably provide the ultra-fine and ultra-regularparticles now required for certain applications.

Various methods for reducing the size of particles have been employed.Many use materials such as spheres, rods or more irregular objects(“grinding media”) to crush or beat the material to be reduced (“productmaterial”) to smaller dimensions by processes known as grinding,milling, comminution, or dispersion. Grinding media range greatly insize, from ore crushers that are several inches in diameter, down tomicron-sized particles that are themselves used to mill much smallerparticles. Grinding media also vary greatly in shape, includingspherical, semi-spherical, oblate spherical, cylindrical, diagonal,rods, and other shapes (hereinafter “shaped media”), and irregularnatural shapes such as grains of sand.

Grinding media are used in various devices such ball mills, rod mills,attritor mills, stirred media mills, pebble mills, etc. Regardless oftheir differences in design, all mills operate by distributing productmaterial around the grinding media and by causing collisions to occurbetween grinding media units such that product material particles arepositioned between the colliding grinding media units. These collisionscause fracturing of product material particles into to smallerdimensions, an effect known descriptively as “size reduction” or“comminution.”

The materials used as grinding media also are frequently used as appliedabrasives. For example, such materials are aggregated in molds and heldtogether by a binder such as molten metal that is poured into the moldand cooled, rendering a “hard body” that is impregnated by the bindermaterial. Hard body materials (also known as “hard bodies”) of this kindare used in deep-well drilling and other applications. Similar processesare used to impregnate the materials in grinding discs and wheels.Various adhesives are used to bind the materials to textiles, papers andother strata for use as sandpapers, sanding belts, and similar products.

Different grinding and milling techniques produce different mean productmaterial particle sizes and uniformity. Gross differences in result areobtained primarily as a function of the size and shape of the grindingmedia. Large grinding media produce relatively large and irregularproduct material particles that are suitable for coarse processes or forfurther refinement by finer processes. Small grinding media can be usedto produce finer and more regular materials as an end in itself, or toalter crystallite aggregates, or to cause mechanochemical alloying, orsome combination thereof. Small grinding media are also used forpolishing, burnishing, and deburring. Mills are sometimes used inseries, with progressively smaller grinding media employed to furtherreduce product material particle size in stages. Variation of the shapeof the grinding media generally affects the regularity of particle size,the efficiency of the milling process, the total cost to achieve a givensize reduction, and other factors. These effects generally are wellknown in the art.

Extremely small particle sizes are proving to be useful for many newapplications. however, the size reduction and regularity necessary forstandardized, acceptable results cannot be achieved by any currentmilling methods. Production now requires alternate particle fabricationmethods such as chemical precipitation, either at a fast rate withunacceptable process variation, or at very slow rates, with unacceptabletime and expense.

Other important effects are obtained by varying the composition of thegrinding media itself. Three material properties dominantly affectgrinding media performance: hardness, mass density, and mechanicaltoughness. Hardness of the grinding medium determines millingeffectiveness, mass density determines milling efficiency, whilemechanical toughness determines product purity and overall processefficiency. Hard materials transfer energy efficiently in collisionswith product material for effective milling, high-density materialsincrease the energy transfer per collision with product material andthus increase milling efficiency, especially for small-dimensiongrinding media, and tough materials can be used for longer periodsbefore they fail and contaminate the product material or otherwiserequire replacement. An ideal milling material is thus very hard, ofvery high mass density, and very tough. Preferably, those qualities willhold as the size of the grinding media is reduced, and regardless of thechosen shape of the grinding media.

The history of engineering materials for grinding media is a history ofaccepting tradeoffs among these material properties, as improvement inone of these factors has previously produced an offsetting reduction inone or more of the others. For example, yttria-stabilized zirconia showsgood mechanical toughness, but with low mass density. Various metalmedia have relatively high mass density, but low mechanical toughness.Carbides showed extreme hardness and mass density, even in smalldimensions, but with unavoidable media failures that cause unacceptableproduct contamination and more general process failures that areincompatible with many applications.

U.S. Pat. No. 5,407,564 (Kaliski) is illustrative. Kaliski discloses arange of high mass density, single-element carbides selected fromtungsten, thallium, niobium, and vanadium in sizes ranging between 10and 100 microns with a requirement of high theoretical density. AsKaliski explains, high theoretical density, nonporous materials areneeded. These materials showed impressive results in producing fine andregular product material in small quantities under controlled laboratoryconditions. Duplication of his example showed his invention to causecontamination of the milled product, as longer-term and higher-volumeproduction attempts failed due to lack of mechanical toughness thatcaused metallic and other contamination of product material. Highdensity ceramics without metal binders, such as tungsten carbidecombined with tungsten di-carbide, also are disclosed by Kaliski as ameans to obtain high milling efficiency but with contamination ofproduct material from the grinding media. Kaliski specificallyrecommends choosing among his claimed materials to select those whosecontaminants provide the most good, or at least do the least damage, tothe milled product. These materials changed the nature of but did notresolve the product material contaminant issue, and did not solve themechanical toughness problem. Rather, these materials tended to fail bydegradation into hard, fine and irregular shards that acted as abrasivesin the media mill, contaminating the product and on one occasionseriously damaging the mill itself.

U.S. Pat. No. 5,704,556 (McLaughlin) discloses ceramic grinding mediawithout metal binders in dimensions of less than 100 microns diameter.While these materials are acceptably hard, and show greater mechanicaltoughness than those disclosed in Kaliski, they lack adequate densityfor many applications or for optimum efficiency in others.

The inventor of the present invention made an effort to make suitablegrinding media from available spherical carbides, of which only singleelement carbides are known in the art. Tungsten carbide/tungstendi-carbide spheres were purchased in conformance to Kaliski'sspecification and used in a shaker mill, but comminution to the degreecited by Kaliski was not evident. Plasma-processed spherical tungstencarbide/tungsten di-carbide was also purchased from another source, inconformance to Kaliski's specification, in sufficient quantity to teston a production scale. This grinding media fractured due to insufficientmechanical toughness, contaminating the product and extensively damagingthe media mill. Tungsten carbide failed due to the lack of mechanicaltoughness despite experimental variation of media velocity, flow rate,material volume, and other milling variables. Grinding media material inconformance to Kaliski's specification was obtained from severaldifference sources worldwide, but differences in sourcing produced nosignificant difference in results. In all attempts with all materialssupplied to the Kaliski specification, the level of productcontamination was a limitation on usefulness.

U.S. Pat. No. 2,581,414 (Hochberg), U.S. Pat. No. 5,478,705 (Czekai),and U.S. Pat. No. 5,518,187 (Bruno) disclose polymer grinding mediawhich show high mechanical toughness and cause relatively benign productmaterial contamination upon grinding media failure. However, they showlow hardness and density relative to ceramics. Polymer grinding mediathus can be useful in milling relatively soft product materials that aresensitive to product contamination, and in industries that arerelatively insensitive to processing cost, such as in drug processing orin dispersing biological cells for analysis, but they are notappropriate for the majority of industrial applications.

U.S. Pat. Nos. 3,690,962, 3,737,289, 3,779,745, and 4,066,451 (all toRudy) disclose certain multi-carbides for use as cutting tools. Althoughthe multi-carbides disclosed showed a combination of hardness, densityand mechanical toughness that promised to be useful for milling, theknown geometries for available multi-carbide materials rendered themincompatible with such use. Difficulties included the large size ofmulti-carbide material that is produced by current manufacturingmethods, and difficulty in machining or otherwise manipulating thematerial into sizes and shapes useful for milling due in part to itshardness and mechanical toughness.

V. N. Eremenko, et al, “Investigations of alloys or the ternary systemsW—HfC—C and W—ZrC—C at subsolidus temperatures,” Dokl. Akad. Nauk. Ukr.SSSR, Ser. A No. 1, 83-88 (1976); L. V. Artyukh, et al, “Physicochemicalreactions of tungsten carbide with hafnium carbide,” Izv. Akad. NaukSSSR, Neorg. Mater., No. 4, 634-637 (1976); and T. Ya. Velikanova, etal, “Effect of alloying on the structure and properties of cast WC1-xMaterials,” Poroshkovaya Metallurgiya, No. 2 (218), 53-58, (1981) teachhow sensitive the properties of single element carbides can be to smalladditions of other carbide forming elements. This fact has greatlyinhibited research into multi-carbide elements.

As summarized above, the grinding media of the prior art all suffer sometechnical disadvantage resulting in a proliferation of grinding mediamaterials creating a significant economic burden and also resulting intechnically inferior milled products due to contamination.

SUMMARY OF THE INVENTION

Briefly stated, grinding media includes shaped media, such as spheres orrods, ranging in size from 0.5 micron to 100 mm in diameter. The mediaare of a multi-carbide material consisting essentially of two differentcarbide-forming elements and carbon, either with or without an elementalform of a carbide-forming element. The media have extremely high massdensity, extreme hardness, and extreme mechanical toughness.

According to an embodiment of the invention, grinding media include amulti-carbide material consisting essentially of carbon and at least twodifferent carbide-forming elements wherein the multi-carbide material isformed into shaped grinding media ranging in size from 0.5 micron to 100mm in diameter.

According to an embodiment of the invention, a method for makinggrinding media includes the step of forming the media from amulti-carbide material consisting essentially of carbon and at least twodifferent carbide-forming elements wherein the multi-carbide material isformed as grinding media for use in a media mill.

According to an embodiment of the invention, a method for making spheresfor use in cladding materials includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and atleast two different carbide-forming elements.

According to an embodiment of the invention, a method for making spheresfor use in surfacing material includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and atleast two different carbide-forming elements.

According to an embodiment of the invention, a method for making spheresfor use in hard body materials includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and atleast two different carbide-forming elements.

According to an embodiment of the invention, a method for makinggrinding media includes the step of forming the media from amulti-carbide material consisting essentially of carbon and one elementselected from the group consisting of chromium, hafnium, niobium,tantalum, titanium, tungsten, molybdenum, vanadium, and zirconium, alongwith the elemental metal of the carbide.

According to an embodiment of the invention, a method for making spheresfor use in cladding material includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and oneelement selected from the group consisting of chromium, hafnium,molybdenum, niobium, rhenium, tantalum, thallium, titanium, tungsten,vanadium, and zirconium, along with the elemental metal of the carbide.

According to an embodiment of the invention, a method for making spheresfor use in surfacing material includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and oneelement selected from the group consisting of chromium, hafnium,molybdenum, niobium, rhenium, tantalum, thallium, titanium, tungsten,vanadium, and zirconium, along with the elemental metal of the carbide.

According to an embodiment of the invention, a method for making spheresfor use in hard body material includes the step of forming the spheresfrom a multi-carbide material consisting essentially of carbon and oneelement selected from the group consisting of chromium, hafnium,molybdenum, niobium, rhenium, tantalum, thallium, titanium, tungsten,vanadium, and zirconium, along with the elemental metal of the carbide.

According to an embodiment of the invention, a method for milling aproduct in a media mill includes the step of using media consistingessentially of a multi-carbide material which consists essentially ofcarbon and at least two carbide-forming elements wherein themulti-carbide is formed as media for use in a media mill.

According to an embodiment of the invention, a method for milling aproduct in a media mill includes the step of using carbide mediaconsisting essentially of carbon and one element selected from the groupconsisting of chromium, hafnium, molybdenum, niobium, rhenium, tantalum,thallium, titanium, tungsten, vanadium, and zirconium, along with theelemental metal of the carbide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows particles produced according to the prior art.

FIG. 2 shows particles produced according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention, a compound is formed from acombination of carbon and two or more different carbide-forming elements(“multi-carbide material”, defined more fully below). Multi-carbidematerials have extreme hardness, extreme density, and extreme mechanicaltoughness. In the present invention, the selection of carbide-formingelements of the multi-carbide materials, and the precise proportionalcomposition for any combination of those elements, is modified to alterthe properties of the material. Multi-carbide material is combined withone or more elemental metals of the chosen carbide to alter ductilityand other properties of the material. Multi-carbide material is formedeffectively and efficiently into a variety of shaped media, preferablyinto spheres, by the use of novel manufacturing methods.

The manufacturing method of the present invention maintains properelement composition to optimize desired material properties, producesuseful shaped media, avoids crushing or other degradation of thematerial to create said shaped media, and greatly lowers manufacturingcost to produce shaped media formed from such material while improvingthe quality of the material obtained. The manufacturing method producessmall and regular spheres of optimized multi-carbide material that issuitable for use as grinding media in media mills (“multi-carbidegrinding media”). The multi-carbide grinding media of the presentinvention are used in shaped media ranging in size from 100 mm or moredown to 0.5 microns or less while maintaining their effective materialproperties. The multi-carbide grinding media are used in media mills andother extant milling processes of varying design and capacity. By suchuse of such multi-carbide grinding media, greater product material sizereduction, size regulation, and purity can be achieved than byutilization of extant milling media materials.

Such use improves the efficiency and outcome of current particle sizereduction methods. Less effective methods could be used as preliminaryprocess steps to produce particles of relatively great size andirregularity, with those particles being further refined by theinvention.

The multi-carbide grinding media of the present invention are usedeffectively in a variety of applications other than media mills, such asthe manufacture of hard bodies, grinding wheels, abrasive papers andtextiles, cladding materials, and hard coating materials.

The invention permits the manufacture of materials in dimensions andpurities that previously were unattainable (“ultra-fine particles”).Ultra-fine particles will enable the manufacture of products previouslyunattainable, or attainable only by less effective or more expensivemethods. Examples include sub-micron sized oxides, such as oxides oftitanium. Reduction of certain oxides of titania with sufficiently lowimpurities causes that compound to exhibit special properties includinghigh transparency. Fine size reduction of pigments improve theefficiency of color distribution in dyes and paints. Similar results areobtained by high refinement of varnishes and other finishes. Ultra-fineparticles of certain metals and other materials, such as cobalt,hydrides, molybdenum, nitrides, titanium, tungsten, and various alloysand other compounds of the same, will permit the manufacture of thosematerials at previously-unachieved economic or performance propertiesand in superalloy and other combinations not previously obtainable.Diamond particles can be reduced to dimensions not previously obtainabledue to their hardness relative to known grinding media, permitting moreefficient use of diamond particles at reduced cost. Ultra-fine particleswill become available that can be formed by molding, electrostaticdeposition and other known methods into microelectromechanical productsand other micron-scale devices that previously were obtainable only byetching of glass or silicon or other semiconductors. Ultra-fineparticles can be introduced to certain liquids to form fluids thatexhibit special properties of heat transmission, solubility and otherqualities.

Through use of the invention, samples produced either by more coarsemilling or by high-rate precipitation are further refined throughmilling process with multi-carbide grinding media to preferredspecifications at high speed and relatively low cost. Other valuablematerials are made uniquely possible by the claimed methods of theinvention.

The invention also permits the manufacture of ultra-fine particles withgeometries superior to those achieved by known manufacturing methods.For example, chemical precipitation can create particles of certainmaterials in extremely small dimensions. Those particles, however,generally exhibit smooth and rounded shapes. FIG. 1 shows particles thatwere assembled atomistically by precipitation. Such particles are alsotypical of those particles produced by known means such as sol gel,vapor phase condensation, etc. The science dealing with the surfacetopography of particles speaks in terms of a fractured surface which hasdiscernible cleavage facets and cleavage steps. These two features arespecifically absent from the particles produced by the known processingmethods for producing very small particles. Another missing feature inparticles produced according to prior art methods is concavity.Concavity is defined as that condition where some portion of the surfacelies beneath the surrounding surface. In precipitated particles, thesurface is bulbulous, meaning that a portion of the surface protrudesabove the surrounding surface such as is always true in the case of asphere.

As shown in FIG. 2, ultra-fine particles produced by milling accordingto the present invention exhibit more angular geometries with cleavedsurfaces and angular intersecting surfaces that exhibit higher activityrelative to the materials formed by other means, causing ultra-finemilled particles to tend to exhibit superior chemical and mechanicalproperties over particles of similar size and dimension that aremanufactured by precipitation and similar methods. Note the corners,flat edges, etc. of the very small particles produced by the millingmethod of the present invention.

A catalyst produced according to the present invention is less than30×10⁻⁹ meters in all dimensions and possesses cleaved surfaces, thecatalyst being uniquely distinguishable by its particle surface featureshaving a preponderance of cleavage facets and/or cleavage steps, thecatalyst alternatively being uniquely distinguishable by the acutance ofa preponderance of intersecting surfaces in which the arc length of theedge is less than the radius of the edge, the catalyst alternativelybeing uniquely distinguishable by surface concavities greater than 5% ofthe particle diameter, the catalyst alternatively being uniquelydistinguishable by the acutance of a preponderance of intersectingsurfaces in which the included angle of the edge radius is about, orless than, the included angle of the intersecting surfaces.

Intermetallic particles produced according to the present invention haveless than 30×10⁻⁹ meters in all dimensions and possess cleaved surfaces.The product is uniquely distinguishable by its particle surface featureshaving a preponderance of cleavage facets and/or cleavage steps, theproduct alternatively being uniquely distinguishable by the acutance ofa preponderance of intersecting surfaces in which the arc length of theedge is less than the radius of the edge, the catalyst alternativelybeing uniquely distinguishable by surface concavities greater than 5% ofthe particle diameter, the product alternatively being uniquelydistinguishable by the acutance of a preponderance of intersectingsurfaces in which the included angle of the edge radius is about, orless than, the included angle of the intersecting surfaces.

The grinding media of the present invention are also useful in otherfields. Examples include the manufacture of “hard bodies” for drillingor grinding, laser cladding and other cladding processes, use as surfacematerials, and other applications. For instance, grinding media are usedwithout media mills as a component of alloys to be applied to surfacesfor improved wear resistance. Two common methods of applying suchprotective coatings are known as cladding and surfacing. Each of thesehave many methods employed, the choice of which depending on the objectand alloy to be treated. Generically, binder materials such as polymersor metals are used to hold grinding media onto the surface of the objectbeing treated by cladding or surfacing. The binder materials are meltedor cast into place along with the grinding media material which itselfis not melted during the cladding or surfacing operation. Typicalmelting methods include laser, furnace melting, welding tubes and plasmaheat sources. When in use, the binder material itself often cannotwithstand the wear imposed on the surface by the operating environmentsuch as in oil well drilling. This binder wear exposes the grindingmedia to the surface, thereby providing a wear resisting surfaceprotection. These same surfaces are often exposed to very high shockimpacts which the grinding media is able to withstand.

To create multi-carbide grinding media, a compound (“multi-carbidematerial”) is formed from carbon and at least two carbide-formingelements. U.S. Pat. Nos. 3,690,962, 3,737,289, 3,779,745, and 4,066,451(all to Rudy), incorporated herein by reference, disclose how to makesuch multi-carbide materials for use as cutting tools.

In an embodiment of the invention, the multi-carbide material is formedfrom carbon and carbide-forming elements selected from the groupconsisting of chromium, hafnium, molybdenum, niobium, rhenium, tantalum,thallium, titanium, tungsten, vanadium, zirconium, and any other carbideforming element. Multi-carbide material can be formed either with orwithout some of the carbide-forming elements not being fully carburizedand thus remaining in the material in its elemental state. Themulti-carbide material can contain a certain amount of impurities andother extraneous elements without significantly affecting its materialproperties.

The production of spheres from irregular shaped particles can beachieved by various means. One common method of processing ultrahighmelting point materials into spheres is with the use of a thermal plasmatorch. Such a torch can operate at temperatures well beyond the meltingpoint of all multi-carbide materials. Other methods, such as meltatomization or arc melting, are known to those familiar with the art andthere is no intention to limit the practice to just the use of thesenamed methods. In short, any known technique for applying heat whichbrings the material to its melting point will work. How to form othershaped media is also known in the art.

The known methods of forming spheres from carbides also form sphereswhen the known methods are applied to multi-carbide materials, but theacceptable spheres amount to approximately 40% of the total produced. Anew method for producing spheres from multi-carbide materials wastherefore developed. According to an embodiment of the invention, themethod for producing spheres from multi-carbide materials is as follows.The multi-carbide material is formed into spheres preferably by admixingfine particles of the elements intended to comprise the multi-carbidematerial in appropriate ratios, by adequately mixing the components, bymaintaining the stability of the mixture by introduction of an inertbinding agent, by subdividing the mixture into aggregates each having amass approximately equal to that of the desired sphere to be formed, byapplying heat to the subdivided aggregate sufficient to cause itselements to fuse, and by cooling the fused sphere in a manner thatpreserves its spherical shape. This manufacturing process is used tomake small and regular spheres that are composed of multi-carbidematerial. Spheres of very small diameters, i.e., less than 500 micronsdiameter and down to 0.5 microns diameter, with regular geometries andpredictable, optimized compositions can be produced.

Spheres of multi-carbide material can be formed in this manner by theuse of a thermal plasma torch or vertical thermal tube to raise thetemperature of the multi-carbide particles above their melting point asthey pass through the plasma or down the tube. Other methods that can soraise the temperature of the multi-carbides, such as melt atomization orarc melting, also should be effective.

Such spheres can be utilized as grinding media in media mills(“multi-carbide grinding media”), as the grinding medium in a hard bodydrill bit or grinding wheel, as the abrasive medium for “sand blasting”shaping techniques, and in other applications.

Shapes other than spheres can be formed. For example, a variety ofshapes can be formed by molding and sintering sufficiently smallparticles of the multi-carbide material. The geometry of such shapes canbe varied nearly arbitrarily to achieve different grinding properties.The manufacturing process is an improvement over the current art in thatit forms multi-carbides by processes that better mix and do not vaporizeelements during manufacture, improving predictability and performancecharacteristics of the produced material; and that do not crack orotherwise degrade the material as it is formed into useful shapes, toimprove the mechanical toughness of the produced material.

The multi-carbide grinding media, of whatever shape, can be used inmedia mills to achieve efficient and thorough comminution of materialswith high purity due to the extreme hardness, extreme density, andextreme mechanical toughness of the material, independent of size orshape. In such applications, particles of product material to be reducedin size are admixed with the colliding grinding media. The productmaterial particles, interspersed between the grinding media units, arerapidly reduced in size. Reductions to controlled dimensions as small as10⁻⁹ meters can be achieved and readily reproduced with the rightcombination of initial source material, grinding media and media mill orother reduction process. Due to the engineered material properties ofthe multi-carbide grinding media, the wear rates of the grinding mediaunits are extremely low and their grinding effectiveness is very high,enabling the efficient conversion of coarse particles into extremelysmall product size while maintaining high purity. That is, themulti-carbide grinding media deliver virtually no contamination to theproduct material.

Separation of product from the multi-carbide grinding media isaccomplished by various means known in the art, such as washing andfiltering or gravity separation. The product particles are much smallerthan the grinding media, so separation can be accomplished efficientlyand effectively.

Selection of appropriate grinding media material is critical to outcome.Very small variations in the chemical composition of a material can havea great effect upon its performance as a grinding or milling medium.Changes of <0.1 at % of a given element in a carbide have been shown tocause changes of 40% or more in hardness, mechanical toughness, or otherimportant property of the compound.

All of the above compositional and processing considerations forproducing microspheres of superior performance for milling also applyfor producing spheres of the present invention for laser cladding, othersurfacing techniques, and hard bodies.

For example, the media of the present invention include mill media ofany geometry composed of multiple carbide-forming elements, with carbon,having a density greater than 8 gm/cc and a combination of hardness andtoughness sufficient to permit use in a media mill without contaminationof the milled product to an amount greater than 800 ppm.

According to the present invention, a method for making spheres,composed of multiple carbide-forming elements, with carbon, for use asmill media, or in cladding material, as surfacing material, or in hardbody materials containing these spheres, includes the steps of:

(a) obtaining fine particles of appropriate compositions to form thedesired composition;

(b) admixing the particles in appropriate ratios to form the desiredcomposition and for adequate mixing of components;

(c) subdividing the mixture into aggregates each having a weight aboutthat of the desired sphere size range; and

(d) fusing the aggregates to at least 90% theoretical density by anymeans providing temperature, and time at temperature, appropriate forfusion of the components.

According to the present invention, a method for producing fine oxidesof any metal but in particular titanium, being of a size less than 3microns and including down to 1×10⁻⁹ using larger particles of oxides oftitanium, includes the steps of:

(a) obtaining large particles of oxides, especially of titanium, becausesuch oxide particles are typically much cheaper to procure than fineparticles of oxides of titanium, hereinafter such particles being termedfeed oxides;

(b) processing the feed oxides in a media mill using spheres ofmulti-carbide materials with a mass density greater than 8 gm/cc and ahardness and toughness sufficient so as not to contaminate the milledoxides of titanium to a degree greater than 200 ppm; and

(c) processing the feed oxides at an energy intensity to cause sizereduction of the feed oxide, in a dry or wet media mill, for a period oftime sufficient to reduce the particle size to the preferred size. Suchoxides are useful for applications such as pigments, fillers, gassensors, optronic devices, catalyst, and the manufacture of ceramics,manufacture of components, while being more economic to produce thanthose obtained by other methods.

According to the present invention, a method for producing highlytransparent oxides of titanium includes the steps of:

(a) obtaining a slurry of not adequately transparent titania;

(b) processing the titania slurry in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient to not contaminate the milled oxidesof titanium to a degree greater than 100 ppm; and

(c) processing the slurry until the size distribution of the particleshas a D100 of 90×10⁻⁹ meters or less.

According to the present invention, a method for producing titaniummetal includes the steps of:

(a) obtaining titania feed material, where the feed material is from ahigh purity source such as readily available chloride processed titania;

(b) processing the titania in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milled oxidesof titanium to a degree greater than 800 ppm;

(c) processing the titania at an energy intensity to cause sizereduction of the feed oxide, in a dry or wet media mill, for a period oftime sufficient to reduce the particle size to about 200×10⁻⁹ meters orless;

(d) chemically reducing the titania to titanium metal using a reducingagent such as hydrogen in combination with another reducing agent, ifneeded, such as a carbothermic reduction agent such as CO or carbonunder conditions suitable for oxide reduction without the formation oftitanium carbide;

(e) either removing the titanium metal from the reduction equipmentwithout exposure to oxygen or nitrogen under conditions causingoxidation or nitridation of the ultrafine titanium metal or raising thetemperature of the ultrafine titanium metal to cause fusion of theparticles before removal from the reduction equipment. Other reducingagents are known in the art.

The present invention can be used for producing diamond particles ofless than about 100×10⁻⁹ meters in all dimensions and, if desired, of atight particle size distribution, with the diamond particles beingusable for CMP (chemical mechanical polishing) and other polishingapplications. According to the present invention, a method for producingsuch diamond includes the steps of:

(a) obtaining industrial diamonds of suitable feed material size;

(b) processing the diamonds in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient cause size reduction of the diamondmaterial;

(c) processing the diamonds at an energy intensity to cause sizereduction of the diamond particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to between about100×10⁻⁹ meters and about 2×10⁻⁹ meters;

(d) purifying the processed diamonds, if necessary to removecontaminants, by chemical dissolution of impurities or by other methodsknown in the art.

According to the present invention, a method for producing devices ofsilicon or other semiconductors or other materials, of micro ornanoscale dimensions, typically called MEMS, by building the device withultrafine particles rather than substractively forming the device fromsolid semiconductor material with etching or other methods, includes thesteps of:

(a) obtaining particulate feed material of the desired composition orcombinations of particulate materials to be composed into a targetcomposition;

(b) processing the feed material in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milled feedmaterial to a degree greater than 200 ppm;

(c) processing the feed material at an energy intensity to cause sizereduction, in a dry or wet media mill, for a period of time sufficientto reduce the particle size to about 200×10⁻⁹ meters or less and morepreferably to 50×10⁻⁹ meters or less;

(d) forming the processed particulates into a molded article, by meansknown in the art such as pressure molding, injection molding, freezemolding, electrophoretic shaping, electrostatic deposition and otherknown methods; whereby the forming method allows for creation of uniqueMEMS devices whereby different parts of the structure can have differentmaterials of construction; and

(e) fusing the molded article to sufficient density to have propertiesadequate for the intended performance of the device, where suchproperties are determined specifically by the design application.

According to the present invention, a method for producing fine SiC of asize less than 1 micron and including down to 0.001 microns using largerparticles of SiC includes the steps of:

(a) obtaining large particles of SiC because such large particles aretypically much cheaper to procure than fine particles of SiC, theseparticles being termed feed particles;

(b) processing the feed particles in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 600 ppm; and

(c) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; with such particles being useful for the manufacture of siliconcarbide ceramic bodies, ceramic bodies containing silicon carbide in thecomposition, applications such as pigments, polishing compounds, polymerfillers, sensors, catalyst, and the manufacture of ceramics, manufactureof components and also being more economic than that obtained by othermethods.

According to the present invention, a method for producing fine Al2O3being of a size less than 1 micron and including down to 0.001 micronsusing larger particles of Al2O3 includes the steps of:

(a) obtaining large particles of Al2O3. Such large particles aretypically much cheaper to procure than fine particles of Al2O3. Theseparticles are termed “feed particles.”

(b) processing the feed particles in a media mill using spheres ofmulti-carbide materials with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 600 ppm; and

(c) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize. Such particles are useful for the manufacture of alumina ceramicbodies, ceramic bodies containing alumina in the composition,applications such as pigments, polishing compounds, polymer fillers,sensors, catalyst, and the manufacture of ceramics, manufacture ofcomponents and also are more economic than that obtained by othermethods.

According to the present invention, a method for producing nanofluidshaving suspended particles with a size distribution of D50=30×10⁻⁹ orless includes the steps of:

(a) obtaining particulate feed material of the desired composition;

(b) processing the feed material in a media mill using spheres ofmulti-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient to not contaminate the milled feedmaterial to a degree greater than 400 ppm;

(c) processing the feed material at an energy intensity to cause sizereduction, in a dry or wet media mill, for a period of time sufficientto reduce the particle size to a milled product of about 200×10⁻⁹ metersor less and more preferably to 50×10⁻⁹ meters or less and mostpreferably to 10×10⁻⁹ meters or less;

(d) concentrating the milled product in suitable carrier fluid, suchcarrier fluids being specified by the application and including water,oil, and organics, with the degree of concentration of particulatematerial in the fluid being specified by the application.

According to the present invention, a method for producing fine tungstenparticles of a size less than 400×10⁻⁹ meters and including down to1×10⁻⁹ meters using larger particles of tungsten, including the stepsof:

(a) obtaining large particles of tungsten because large particles aretypically much cheaper to procure than fine particles of tungsten, withthe particles being termed feed particles;

(b) nitriding the feed material, such nitride being known to be brittle,by known methods of nitriding such as heating tungsten in dissociatedammonia at 500 degrees C. for a length of time proportionate to the feedmaterial size but sufficient to cause nitridation;

(c) processing the nitrided feed particles in a media mill using spheresof multi-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 900 ppm;

(d) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; and

(e) if desired, denitriding the tungsten nitride particulates by heatingto about 600 degrees C. or higher by methods now known in the art. Suchparticles are useful for the manufacture of tungsten bodies, tungstenalloy bodies, ceramic bodies containing tungsten in the composition,applications such as pigments, polishing compounds, electronic inks,metallo-organic compounds, polymer fillers, sensors, catalyst, and themanufacture of metal-ceramics, manufacture of components and are alsomore economic than that obtained by other methods.

According to the present invention, a method for producing tungstencomponents, or tungsten alloy components, from the fine tungstenparticles produced by the method detailed in the preceding paragraph,includes the steps of:

(a) obtaining nitrided tungsten milled product of a size less than400×10⁻⁹ meters and more preferably less than 100×10⁻⁹ meters and mostpreferably of less than 50×10⁻⁹ meters;

(b) producing tungsten metal components by powder metallurgy processingby consolidation and forming the tungsten nitride prior todenitridation;

(c) denitriding the tungsten nitride component during heating tosintering temperatures with the release of nitrogen contributing toflushing residual gases from between the particles; and

(d) sintering the formed component at temperatures proportionate to theparticle size, with these temperatures being substantially less than nowrequired in the art for commercially available tungsten powders.

According to the present invention, a method for producing finemolybdenum particles of a size less than 400×10⁻⁹ meters and includingdown to 1×10⁻⁹ meters using larger particles of molybdenum includes thesteps of:

(a) obtaining large particles of molybdenum, such large particlestypically being much cheaper to procure than fine particles ofmolybdenum, said particles being termed feed particles;

(b) nitriding the feed material, such nitride being known to be brittle,by known methods of nitriding such as heating molybdenum in dissociatedammonia at about 500 degrees C. for a length of time proportionate tothe feed material size but sufficient to cause nitridation;

(c) processing the nitrided feed particles in a media mill using spheresof multi-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient to not contaminate the milledparticles to a degree greater than 900 ppm;

(d) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; and

(e) if desired, denitriding the molybdenum nitride particulates byheating to about 600 degrees C. or higher by methods now known in theart. Such particles are useful for the manufacture of molybdenum bodies,molybdenum alloy bodies, ceramic bodies containing molybdenum in thecomposition, electronic inks, metallo-organic compounds, applicationssuch as pigments, polishing compounds, polymer fillers, sensors,catalyst, and the manufacture of metal-ceramics, manufacture ofcomponents and also are more economic than particles obtained by othermethods.

According to the present invention, a method for producing molybdenum ormolybdenum alloy components from particles produced according to themethod of the preceding paragraph include the steps of:

(a) obtaining nitrided molybdenum milled product of a size less than400×10⁻⁹ meters and more preferably less than 100×10⁻⁹ meters and mostpreferably of less than 50×10⁻⁹ meters;

(b) producing molybdenum metal or alloy components by powder metallurgyprocessing by consolidation and forming the molybdenum nitride prior todenitridation;

(c) denitriding the molybdenum nitride during heating to sinteringtemperatures with the release of nitrogen contributing to flushingresidual gases from between the particles; and

(d) sintering the formed component at temperatures proportionate to theparticle size, where these temperatures are substantially less than nowrequired in the art for commercially available molybdenum powders.

According to the present invention, a method for producing fine cobaltparticles or cobalt nitride particles being of a size less than 5microns and including down to 1×10⁻⁹ meters using larger particles ofcobalt includes the steps of:

(a) obtaining large particles of cobalt or cobalt nitride, such largeparticles typically being gas atomized and therefore much cheaper toprocure than fine particles of cobalt or cobalt nitride, with suchparticles being termed feed particles;

(b) nitriding the feed material, if not already nitrided, such nitridebeing known to be brittle, by known methods of nitriding such as heatingcobalt in dissociated ammonia at about 600 degrees C. for a length oftime proportionate to the feed material size but sufficient to causenitridation;

(c) processing the nitrided feed particles in a media mill using spheresof multi-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 500 ppm;

(d) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; and

(e) if desired, denitriding the cobalt nitride particulates by heatingto about 600 degrees C. or higher by methods now known in the art. Suchparticles are useful for the manufacture of catalyst, alloy bodiescontaining cobalt, ceramic bodies containing cobalt in the composition,electronic inks, metallo-organic compounds, applications such aspigments, polishing compounds, polymer fillers, sensors, catalyst,promoters, the manufacture of superalloy components containing cobalt,for use in the hard metals industries where cobalt is a binder metal andalso are more economic to produce than those obtained by other methods.

According to the present invention, a method for producing fine metalparticles from metal nitrides, being of a size less than 20 microns andincluding down to 1×10⁻⁹ meters using larger particles of metalsincludes the steps of:

(a) obtaining large particles of metal or metals nitride from that groupof metals having nitrides that dissociate when heated from 300 degreesC. to about 900 degrees C., such large particles typically being gasatomized and therefore much cheaper to procure than fine particles ofmetals or metals nitride, such particles being termed feed particles;

(b) nitriding the feed material, if not already nitrided, such nitridebeing known to be more brittle than metal which is ductile, by knownmethods of nitriding such as heating metals particles in dissociatedammonia at a temperature sufficient to cause nitridation for a length oftime proportionate to the feed material size but sufficient to causenitridation;

(c) processing the nitrided feed particles in a media mill using spheresof multi-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 900 ppm;

(d) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; and

(e) if desired, denitriding the metals nitride particulates by heatingto about 600 degrees C. or higher by methods now known in the art. Suchparticles are useful for the manufacture of catalyst, alloy bodiescontaining metals, ceramic bodies containing metals in the composition,electronic inks, metallo-organic compounds, applications such aspigments, polishing compounds, polymer fillers, sensors, catalyst,promoters, the manufacture of superalloy components, the manufacture ofmetal components combining various metals processed by this claim, foruse in the hard metals industries where metals is a binder metal andalso are more economical to produce than those obtained by othermethods.

According to the present invention, a method for producing fine metalparticles or metal hydride particles from metal hydrides such astitanium and tantalum, being of a size less than 300×10⁻⁹ meters andincluding down to 1×10⁻⁹ meters using larger particles of metalsincludes the steps of:

(a) obtaining large particles of metal hydrides from that group ofmetals forming hydrides that dissociate when heated, such largeparticles typically being pressure hydrided and therefore much cheaperto procure than fine particles of metals or metal hydrides, with suchparticles being termed feed particles;

(b) processing the hydrided feed particles in a media mill using spheresof multi-carbide material with a mass density greater than 8 gm/cc and ahardness and toughness sufficient not to contaminate the milledparticles to a degree greater than 900 ppm;

(c) processing the feed particles at an energy intensity to cause sizereduction of the feed particles, in a dry or wet media mill, for aperiod of time sufficient to reduce the particle size to the preferredsize; and

(d) if desired, dehydriding the ultrafine metals hydride particulates byheating to the dehydration temperature by methods now known in the art.Such particles are useful for the manufacture of catalyst, alloy bodiescontaining metals, ceramic bodies containing metals in the composition,electronic inks, metallo-organic compounds, applications such aspigments, polishing compounds, polymer fillers, sensors, catalyst,promoters, the manufacture of superalloy components, the manufacture ofmetal components combining various metals processed by this claim, foruse in the hard metals industries where metals is a binder metal andalso being more economic than that obtained by other means

As discussed in the Background section, the search for an optimalmaterial to be used as mill media has been ongoing. After muchexperimentation and testing, multi-carbides were identified by theinventor as a possible material. Although the multi-carbides disclosedby the Rudy patents showed a combination of hardness, density andmechanical toughness that promised to be useful for milling, the knowngeometries for available multi-carbide materials rendered themincompatible with such use. Difficulties included the large size ofmulti-carbide material that is produced by current manufacturingmethods, and difficulty in machining or otherwise manipulating thematerial into sizes and shapes useful for milling due in part to itshardness and mechanical toughness.

After extensive analysis and experimentation, the effectiveness of usingmulti-carbide grinding media was shown empirically in the followingexperiment. Spheres according to the present invention were formed bytaking material composed of Ti, W, and C and preparing spheres 150microns in diameter. The test composition in this example was 86.7 wt %tungsten, 4.5 wt % carbon, and the balance titanium. Agglomerates ofparticulates of this test composition were spheridized in an RF Plasmaspray unit. The density of the material was confirmed as being the sameas the multi-carbide material that was sought to be made.

The multi-carbide spheres of the present invention were then subjectedto hardness testing. A compression test was employed in which a singlesmall sphere was isolated between two pieces of ground tungsten plateand a force was applied to one of the plates. The intention was toincrease the applied pressure until the sphere fragmented due to theextreme load at the point contact between the plate and the sphere.Unexpectedly, spheres of the test composition did not fracture, butinstead embedded into the tungsten plate, demonstrating hardness of thetest material well above that of pure tungsten. In a second test,several spheres were positioned between two tungsten plates and the topplate was struck with a weight so as to induce high transitory g-forceson the spheres. None of the spheres fractured, with many of the spheresembedded into the tungsten plate. In two instances of the experiment,the tungsten plate fractured and cleaved, but with no apparent damage tothe spheres. In another experiment, spheres of the test composition wereplaced between two ground glass plates. Upon applying pressure, theglass micro-fragmented around its points of contact with the spheres,but no damage to the spheres was observed.

The multi-carbide spheres were subjected to mechanical toughnesstesting. Spheres of the test composition were placed in a vibratory millwith calcium carbide and agitated for a period of time sufficient tocause significant grinding media degradation by all known grindingmedia. No evidence of contamination by grinding media degradation wasobserved from such use of the resultant spheres, and very fine, regularand pure calcium carbide was obtained.

The multi-carbide spheres were also subjected to testing by use instandard industry processes. The spheres were used in a high-volumemedia mill and operated under nominal industrial production conditionsused to mill titania. Titania is particularly sensitive to discolorationfrom contamination and was chosen to be a sensitive indicator to see ifthe microspheres were able to impart wear without themselves wearingsignificantly. Billions of particles of titania were processed to afinal particle size of approximately 7×10⁻⁸ meters without perceptibleevidence of grinding media degradation.

While testing and processing various materials, impurities wereoccasionally measured to see how the process was working. Tests wereconducted with calcium carbonate processed to less than 100 mm usingstandard media mill operating conditions and the grinding media of theinvention of 120 microns diameter. The contamination level in the milledproduct was measured to be less than 100 ppm, and in some instances,less than 10 ppm. The contamination level is dependent on the substancebeing milled, with calcium carbonate being relatively soft. It isexpected that the contamination level should always be below 300 ppmeven when milling alumina.

While the present invention has been described with reference to aparticular preferred embodiment, it will be understood by those skilledin the art that the invention is not limited to the preferred embodimentand that various modifications and the like could be made theretowithout departing from the scope of the invention as defined in thefollowing claims.

1-76. (canceled)
 77. A method for producing Al2O3 particles of a sizebetween 1×10⁻⁹ meters and 1,000×10⁻⁹ meters, comprising the steps of:(a) obtaining feed particles of Al2O3; and (b) processing said feedparticles in a media mill using spheres comprising multi-carbidematerial with a mass density greater than 8 gm/cc and a hardness andtoughness sufficient not to introduce contamination of the milledparticles to a degree greater than about 600 ppm; said processing beingat an energy intensity to cause size reduction of said feed particlesfor a period of time effective to reduce a size of said feed particlesto between 1×10⁻⁹ meters and 1,000×10⁻⁹ meters.
 78. A method forproducing Al2O3 particles of a size between 1×10⁻⁹ meters and 1,000×10⁻⁹meters, comprising the steps of: (a) obtaining feed particles of Al2O3;and (b) processing said feed particles in a media mill using spherescomprising multi-carbide material which comprise carbon and at least twodifferent carbide-forming elements; said processing being at an energyintensity to cause size reduction of said feed particles for a period oftime effective to reduce a size of said feed particles to between 1×10⁻⁹meters and 1,000×10⁻⁹ meters.
 79. A method according to claim 77,wherein said multi-carbide material includes carbide forming elementswhich are selected from the group consisting of chromium, hafnium,molybdenum, niobium, rhenium, tantalum, thallium, titanium, tungsten,vanadium, and zirconium.
 80. A method according to claim 77, whereinsaid multi-carbide material further includes at least one carbideforming element in its elemental state.
 81. A method according to claims78, wherein said carbide forming elements are selected from the groupconsisting of chromium, hafnium, molybdenum, niobium, rhenium, tantalum,thallium, titanium, tungsten, vanadium, and zirconium.
 82. A methodaccording to claim 78, wherein said multi-carbide material furtherincludes at least one carbide forming element in its elemental state.83. A method for producing Al2O3 particles of a size between 1×10⁻⁹meters and 1,000×10⁻⁹ meters, comprising the steps of: (a) obtainingfeed particles of Al2O3; and (b) processing said feed particles in amedia mill using spheres comprising multi-carbide material whichcomprise carbon and only one carbide-forming element selected from thegroup consisting of chromium, hafnium, molybdenum, niobium, rhenium,tantalum, thallium, titanium, tungsten, vanadium, and zirconium, alongwith the elemental metal of the carbide-forming element; said processingbeing at an energy intensity to cause size reduction of said feedparticles for a period of time effective to reduce a size of said feedparticles to between 1×10⁻⁹ meters and 1,000×10⁻⁹ meters.
 84. A methodaccording to claims 77 or 78, wherein said multi-carbide materialcomprises carbon and one carbide-forming element selected from the groupconsisting of chromium, hafnium, molybdenum, niobium, rhenium, tantalum,thallium, titanium, tungsten, vanadium, and zirconium, along with theelemental metal of the carbide-forming element.
 85. A method accordingto claims 77 or 78, wherein said multi-carbide material consistsessentially of titanium, tungsten, and carbon, in the ratios of fromabout 10 to 90 at % tungsten, from about 2 to 97 at % titanium, and thebalance carbon.
 86. A method according to claims 77 or 78, wherein saidmulti-carbide material consists essentially of about 10 to 40 at %carbon; from about 5 to 50 at % titanium, and the balance beingtungsten.
 87. A method according to claims 77 or 78, wherein saidmulti-carbide material comprises: a carbide consisting essentially offrom about 10 to 40 at % carbon, from about 5 to 50 at % titanium, andthe balance being tungsten; and at least one material taken from thegroup consisting of molybdenum, chromium, and rhenium; wherein said atleast one material is in an amount from 0 to about 20 at %, with thetungsten remaining in the composition being not less than 10 at %.
 88. Amethod according to claims 77 or 78, wherein said multi-carbide materialcomprises from about 20 to 30 at % carbon; from about 5 to 50 at %titanium; from about 0 to 30 at % of at least a first material from thegroup consisting of rhenium, zirconium, hafnium and molybdenum; fromabout 0 to 10 at % of at least a second material taken from the groupconsisting of vanadium, niobium and tantalum; from about 0 to 20 at %chromium; with the balance, but not less than 10 at %, being tungsten.89. A method according to claims 77 or 78, wherein said multi-carbidematerial comprises: (a) from about 15 to 60 at % titanium and firstalloying substituents, wherein said first alloying substituents consistof hafnium, niobium, tantalum and zirconium; and wherein titanium,titanium and niobium, or titanium and niobium and tantalum are presentfrom 0 to 20 at %; wherein titanium or titanium and zirconium arepresent from about 0 to 10 at %; and wherein titanium or titanium andhafnium are present from about 0 to 30 at %; and the balance, if any,being titanium; (b) from about 3 to 47 at % tungsten and second alloyingsubstituents, wherein said second alloying substituents consist ofchromium, molybdenum, vanadium, tantalum and niobium; wherein tungstenor tungsten and chromium are present from about 0 to 5 at %; whereintungsten or tungsten and molybdenum are present from about 0 to 25 at %;wherein tungsten or tungsten and vanadium are present from about 0 to 5at %; and wherein tungsten, tungsten and tantalum, tungsten and niobium,or tungsten and tantalum and niobium are present from about 0 to 20 at%; and the balance, if any, being tungsten; (c) carbon from about 30 to55 at %; (d) wherein the atomic percentages of niobium and tantalum,each alone or in combination, never exceed 20 at %; and (e) wherein thetotal at % of all constituents is 100 at %, all of the constituents ofthe alloy being of normal commercial purity.
 90. A method according toclaims 77, 78, or 83, wherein said media mill is one of a dry media milland a wet media mill.
 91. A method according to claims 77, 78, or 83,further comprising the step of using said processed feed particles inmanufacturing alumina ceramic bodies.
 92. A method according to claims77, 78, or 83, further comprising the step of using said processed feedparticles in manufacturing ceramic bodies containing alumina in theircomposition.
 93. A method according to claims 77, 78, or 83, furthercomprising the step of using said processed feed particles inmanufacturing pigments.
 94. A method according to claims 77, 78, or 83,further comprising the step of using said processed feed particles inmanufacturing polishing compounds.
 95. A method according to claims 77,78, or 83, further comprising the step of using said processed feedparticles in manufacturing polymer fillers.
 96. A method according toclaims 77, 78, or 83, further comprising the step of using saidprocessed feed particles in manufacturing sensors.
 97. A methodaccording to claims 77, 78, or 83, further comprising the step of usingsaid processed feed particles in manufacturing catalysts.
 98. A methodaccording to claims 77, 78, or 83, further comprising the step of usingsaid processed feed particles in manufacturing ceramics.
 99. A methodaccording to claims 77, 78, or 83, further comprising the step of usingsaid processed feed particles in manufacturing varnishes.